The present invention relates generally to an improved clinical technique for catheterization and apparatus for performing same, and more particularly, an improved technique for central venous catheterization.
The sole objective of central venous catheterization is to establish a direct conduit from the exterior of the body to the superior vena cava. Thus, catheterization of the superior cava is invaluable in special circumstances when there is critical necessity to: (1) measure central venous pressure frequently to guide fluid balance endeavors in persons with marginal cardiac or renal reserve; (2) procure aliquots of mixed blood repeatedly for gasometric or biochemical analysis; (3) administer massive volumes of fluids or blood rapidly for resuscitation and ancillary purposes; and (4) infuse intravenously, over long periods of time, hypertonic, acidic, or kindred irritant solutions which would assuredly incite phlebosclerosis were they not diluted right away in the faster stream of central venous channels.
Traditionally, central venous catheterization has been saved as a last resort when other routes were non-existent at the outset or became exhausted. It has been considered preferable to try a safer procedure before using one that carried risks. However, the benefits of using a central insertion site may outweigh the risk because the central venous vein: (1) is closer to the cava; (2) has a constant location; (3) is relatively big; (4) has a fairly large volume flow through it; (5) is less liable to collapse or go into spasm, being kept patulous by fibrous attachments from its walls to adjacent rigid structures; (6) rarely is anomalous or diseased; and (7) is sheltered by the clavicle from ordinary external trauma.
Several techniques have been developed in the past in an attempt to reduce the risks associated with central venous catheterization. One such attempt is the "through the needle" technique for catheterization whereby the patient is first placed in the trendelenburg position (supine with feet higher than head). Then, the skin over and around the subclavian vein is cleaned with antiseptic solution and a sterile field or working area is set-up using sterile towels. A small area of skin (the proposed puncture site) within the sterile field is then anesthetized by injecting a small amount of local anesthetic into the skin using a small hollow needle and syringe. Next, a large (14 gauge 7 cm long) hollow needle with a syringe attached is passed through the anesthetized skin and into the vein. After puncturing the skin, continuous suction is applied to the syringe. By applying continuous suction, entrance into the subclavian vein is signaled by the appearance of blood into the attached syringe. Once the needle is in position, the syringe is removed from the needle and a smaller diameter catheter (16 gauge flexible hollow tube about 50 cm long) is passed through the needle along the course of the vein and into the central venous system (superior vena cava). The needle is then withdrawn over the catheter, leaving the catheter in the puncture site.
There are several distinct disadvantages associated with the utilization of the through needle catheterization techinque. First, because a large needle must be used, there is an increased chance of pneumothorax if the pleura cavity is punctured and a greater chance of air embolus when the syringe is removed from the needle to insert the catheter. In addition, because the needle is larger than the catheter, the puncture wound is not sealed completely by the catheter, increasing the chance of the ingress of air (air embolus) and seepage of blood (hematoma formation) around the catheter. Furthermore, the larger needle the greater the chance of hemorrhage if the subclavian artery is punctured. Because the catheter must pass over the sharp edge of the needle, the tip of the catheter may be seared off into the blood stream causing embolus. Lastly, because the catheter is flexible, it is hard to direct it into the right position during insertion and may have a tendency to buckle or kink when it meets resistance, especially when turning corners. Thus, there has been a need for an improved catheterization technique and apparatus for performing same which overcomes these disadvantages while providing an improved technique as compared to prior conventional techniques.
Alternatively, it is conventional to use an "over the wire" catheterization technique. As with the through needle catheterization technique, the patient is prepared as set forth above. However, a larger (16 gauge 7 cm long) hollow needle with a syringe attached is passed through the anesthetized skin and into the subclavian vein. After puncturing the skin, continuous suction is applied to the syringe the appearance of blood signals entrance into the vein. Next, the syringe is taken off the needle and a long 70 cm guide wire, with a floppy tip and a diameter about equal to the internal diameter of the needle, is passed through the needle, floppy end first, into the vein. The needle is then withdrawn from the patient over the guide wire and a long 50 cm 16 gauge hollow catheter is threaded onto the wire. Next, the wire and the catheter are passed along the inside of the subclavian vein into the central venous system (superior vena cava).
There is a distinct disadvantage associated with the utilization of the above mentioned over the wire catheterization technique, namely that the technique is substantially slower than the through the needle technique. First, the guide wire must be threaded through the needle into the subclavian vein and then the needle removed. Next, the catheter must be threaded onto the wire, and then both are threaded inside of the vein into the central venous system. Finally, after all of the above, the wire is removed. All these steps require substantial time, which may be unavailable and time is of vital importance in an emergency situation. Thus, there has been a need for an improved catheterization technique which overcomes these disadvantages while providing an improved technique as compared to prior techniques.
The present invention is directed to an improved clinical catheterization technique and apparatus for performing same which is superior to conventional methods of central venous catheterization and which offers a combination of quick application, better control of catheter positioning and decreased chances of air embolus, hemorrhage, hematoma formation, catheter embolus and pneumothorax.